Backup power sources provide power to a load during loss of a primary power source. Often times, backup power is provided by batteries or battery packs. Backup power is used in various applications where continuous power is needed, for example, to protect electrical systems from corruption and/or loss of data upon failure of a primary power source. Normally, a primary power source supplies power to the load and also charges the backup batteries (or battery packs) simultaneously. During loss, malfunction or non-operation of a primary power source, the batteries (or battery packs) supply power to the load. For example, a system may experience temporary primary power loss when it is in the process of switching its primary power source from an AC utility line to a backup power generator, or vice versa. This can happen when, for example, voltage supplied by the AC utility line falls below a specified level for some time and then returns to normalcy. It would take some period of time for the backup generator to replace the AC utility line as the primary power source and to raise its output level to sufficiently power the load, during which transition period the backup power source powers the load. Likewise, it would take some time for the AC utility line to replace the backup generator to once again become the primary power source, during which transition period the backup power source powers the load.
A problem with conventional power systems and methods is that when a primary power source (e.g. AC utility line or backup generator) is restored to normalcy, it tries to suddenly step up from providing zero power to providing much heavier power demanded by the load. The primary power converter coupled to the primary power source may not be configured to manage such a sudden and significant load change and may fail to supply power to the load during the transient period. Another problem with conventional power systems and methods is that backup power usage is not properly managed, which causes unnecessary drainage of batteries (or battery packs).